THE SCANDIUM RUTHENIUM PHASE-DIAGRAM

The constitutional diagram of the Sc-Ru system is investigated using m etallography, X-ray diffraction, microprobe and differential thermal a nalysis data as well as alloy melting-point data measured according to the Pirani-Alterthum method. The existence of four intermediate phase s in the system, namely ScRu2 (MgZn2-type structure), ScRu (CsCl), Sc1 1Ru4 (Zr11Os4) and Sc57Ru13 (Sc57Rh13), is substantiated. Sc5Ru3 and S c2Ru were observed for the first time. Their crystal structures were a ttributed by us to the Mn5Si3 and Ti2Ni types respectively. The existe nce of the phase Sc3Ru, mentioned in the literature, was not verified. The ScRu2, ScRu and Sc57Ru13 phases melt congruently with the solidus curve maxima at 1820 degrees C, 1760 degrees C and 1290 degrees C res pectively. The Sc5Ru3, Sc2Ru and Sc11Ru4 phases form by the peritectic reactions at 1300 degrees C, 1160 degrees C and 1130 degrees C respec tively. The formation of the Sc44Ru7 phase is assumed to occur via a s olid state reaction at 950 degrees C. Coordinates of four eutectic poi nts and one eutectoid point are determined.